var WebRtcStreamer = (function() {

  /**
   * Interface with WebRTC-streamer API
   * @constructor
   * @param {string} videoElement - id of the video element tag
   * @param {string} srvurl -  url of webrtc-streamer (default is current location)
  */
  var WebRtcStreamer = function WebRtcStreamer (videoElement, srvurl) {
    if (typeof videoElement === "string") {
      this.videoElement = document.getElementById(videoElement);
    } else {
      this.videoElement = videoElement;
    }
    this.srvurl           = srvurl || location.protocol+"//"+window.location.hostname+":"+window.location.port;
    this.pc               = null;

    this.mediaConstraints = { offerToReceiveAudio: true, offerToReceiveVideo: true };

    this.iceServers = null;
    this.earlyCandidates = [];
  }

  WebRtcStreamer.prototype._handleHttpErrors = function (response) {
      if (!response.ok) {
          throw Error(response.statusText);
      }
      return response;
  }

  /**
   * Connect a WebRTC Stream to videoElement
   * @param {string} videourl - id of WebRTC video stream
   * @param {string} audiourl - id of WebRTC audio stream
   * @param {string} options  -  options of WebRTC call
   * @param {string} stream   -  local stream to send
   * @param {string} prefmime -  prefered mime
  */
  WebRtcStreamer.prototype.connect = function(videourl, audiourl, options, localstream, prefmime) {
    this.disconnect();

    // getIceServers is not already received
    if (!this.iceServers) {
      console.log("Get IceServers");

      fetch(this.srvurl + "/api/getIceServers")
        .then(this._handleHttpErrors)
        .then( (response) => (response.json()) )
        .then( (response) =>  this.onReceiveGetIceServers(response, videourl, audiourl, options, localstream, prefmime))
        .catch( (error) => this.onError("getIceServers " + error ))

    } else {
      this.onReceiveGetIceServers(this.iceServers, videourl, audiourl, options, localstream, prefmime);
    }
  }

  /**
   * Disconnect a WebRTC Stream and clear videoElement source
  */
  WebRtcStreamer.prototype.disconnect = function() {
    if (this.videoElement?.srcObject) {
      this.videoElement.srcObject.getTracks().forEach(track => {
        track.stop()
        this.videoElement.srcObject.removeTrack(track);
      });
    }
    if (this.pc) {
      fetch(this.srvurl + "/api/hangup?peerid=" + this.pc.peerid)
        .then(this._handleHttpErrors)
        .catch( (error) => this.onError("hangup " + error ))


      try {
        this.pc.close();
      }
      catch (e) {
        console.log ("Failure close peer connection:" + e);
      }
      this.pc = null;
    }
  }

  /*
  * GetIceServers callback
  */
  WebRtcStreamer.prototype.onReceiveGetIceServers = function(iceServers, videourl, audiourl, options, stream, prefmime) {
    this.iceServers       = iceServers;
    this.pcConfig         = iceServers || {"iceServers": [] };
    try {
      this.createPeerConnection();

      var callurl = this.srvurl + "/api/call?peerid=" + this.pc.peerid + "&url=" + encodeURIComponent(videourl);
      if (audiourl) {
        callurl += "&audiourl="+encodeURIComponent(audiourl);
      }
      if (options) {
        callurl += "&options="+encodeURIComponent(options);
      }

      if (stream) {
        this.pc.addStream(stream);
      }

                  // clear early candidates
      this.earlyCandidates.length = 0;

      // create Offer
      this.pc.createOffer(this.mediaConstraints).then((sessionDescription) => {
        console.log("Create offer:" + JSON.stringify(sessionDescription));

        console.log(`video codecs:${Array.from(new Set(RTCRtpReceiver.getCapabilities("video")?.codecs?.map(codec => codec.mimeType)))}`)
        console.log(`audio codecs:${Array.from(new Set(RTCRtpReceiver.getCapabilities("audio")?.codecs?.map(codec => codec.mimeType)))}`)

        if (prefmime != undefined) {
          //set prefered codec
          const [prefkind] = prefmime.split('/');
          const codecs = RTCRtpReceiver.getCapabilities(prefkind).codecs;
          const preferedCodecs = codecs.filter(codec => codec.mimeType === prefmime);

          console.log(`preferedCodecs:${JSON.stringify(preferedCodecs)}`);
          this.pc.getTransceivers().filter(transceiver => transceiver.receiver.track.kind === prefkind).forEach(tcvr => {
            if(tcvr.setCodecPreferences != undefined) {
              tcvr.setCodecPreferences(preferedCodecs);
            }
          });
        }


        this.pc.setLocalDescription(sessionDescription)
          .then(() => {
            fetch(callurl, { method: "POST", body: JSON.stringify(sessionDescription) })
              .then(this._handleHttpErrors)
              .then( (response) => (response.json()) )
              .catch( (error) => this.onError("call " + error ))
              .then( (response) =>  this.onReceiveCall(response) )
              .catch( (error) => this.onError("call " + error ))

          }, (error) => {
            console.log ("setLocalDescription error:" + JSON.stringify(error));
          });

      }, (error) => {
        alert("Create offer error:" + JSON.stringify(error));
      });

    } catch (e) {
      this.disconnect();
      alert("connect error: " + e);
    }
  }


  WebRtcStreamer.prototype.getIceCandidate = function() {
    fetch(this.srvurl + "/api/getIceCandidate?peerid=" + this.pc.peerid)
      .then(this._handleHttpErrors)
      .then( (response) => (response.json()) )
      .then( (response) =>  this.onReceiveCandidate(response))
      .catch( (error) => this.onError("getIceCandidate " + error ))
  }

  /*
  * create RTCPeerConnection
  */
  WebRtcStreamer.prototype.createPeerConnection = function() {
    console.log("createPeerConnection  config: " + JSON.stringify(this.pcConfig));
    this.pc = new RTCPeerConnection(this.pcConfig);
    var pc = this.pc;
    pc.peerid = Math.random();

    pc.onicecandidate = (evt) => this.onIceCandidate(evt);
    pc.onaddstream    = (evt) => this.onAddStream(evt);
    pc.oniceconnectionstatechange = (evt) => {
      console.log("oniceconnectionstatechange  state: " + pc.iceConnectionState);
      if (this.videoElement) {
        if (pc.iceConnectionState === "connected") {
          this.videoElement.style.opacity = "1.0";
        }
        else if (pc.iceConnectionState === "disconnected") {
          this.videoElement.style.opacity = "0.25";
        }
        else if ( (pc.iceConnectionState === "failed") || (pc.iceConnectionState === "closed") )  {
          this.videoElement.style.opacity = "0.5";
        } else if (pc.iceConnectionState === "new") {
          this.getIceCandidate();
        }
      }
    }
    pc.ondatachannel = function(evt) {
      console.log("remote datachannel created:"+JSON.stringify(evt));

      evt.channel.onopen = function () {
        console.log("remote datachannel open");
        this.send("remote channel openned");
      }
      evt.channel.onmessage = function (event) {
        console.log("remote datachannel recv:"+JSON.stringify(event.data));
      }
    }

    try {
      var dataChannel = pc.createDataChannel("ClientDataChannel");
      dataChannel.onopen = function() {
        console.log("local datachannel open");
        this.send("local channel openned");
      }
      dataChannel.onmessage = function(evt) {
        console.log("local datachannel recv:"+JSON.stringify(evt.data));
      }
    } catch (e) {
      console.log("Cannor create datachannel error: " + e);
    }

    console.log("Created RTCPeerConnnection with config: " + JSON.stringify(this.pcConfig) );
    return pc;
  }


  /*
  * RTCPeerConnection IceCandidate callback
  */
  WebRtcStreamer.prototype.onIceCandidate = function (event) {
    if (event.candidate) {
      if (this.pc.currentRemoteDescription)  {
        this.addIceCandidate(this.pc.peerid, event.candidate);
      } else {
        this.earlyCandidates.push(event.candidate);
      }
    }
    else {
      console.log("End of candidates.");
    }
  }


  WebRtcStreamer.prototype.addIceCandidate = function(peerid, candidate) {
    fetch(this.srvurl + "/api/addIceCandidate?peerid="+peerid, { method: "POST", body: JSON.stringify(candidate) })
      .then(this._handleHttpErrors)
      .then( (response) => (response.json()) )
      .then( (response) =>  {console.log("addIceCandidate ok:" + response)})
      .catch( (error) => this.onError("addIceCandidate " + error ))
  }

  /*
  * RTCPeerConnection AddTrack callback
  */
  WebRtcStreamer.prototype.onAddStream = function(event) {
    console.log("Remote track added:" +  JSON.stringify(event));

    this.videoElement.srcObject = event.stream;
    var promise = this.videoElement.play();
    if (promise !== undefined) {
      promise.catch((error) => {
      console.warn("error:"+error);
      this.videoElement.setAttribute("controls", true);
      });
    }
  }

  /*
  * AJAX /call callback
  */
  WebRtcStreamer.prototype.onReceiveCall = function(dataJson) {

    console.log("offer: " + JSON.stringify(dataJson));
    var descr = new RTCSessionDescription(dataJson);
    this.pc.setRemoteDescription(descr).then(() =>  {
        console.log ("setRemoteDescription ok");
        while (this.earlyCandidates.length) {
          var candidate = this.earlyCandidates.shift();
          this.addIceCandidate(this.pc.peerid, candidate);
        }

        this.getIceCandidate()
      }
      , (error) => {
        console.log ("setRemoteDescription error:" + JSON.stringify(error));
      });
  }

  /*
  * AJAX /getIceCandidate callback
  */
  WebRtcStreamer.prototype.onReceiveCandidate = function(dataJson) {
    console.log("candidate: " + JSON.stringify(dataJson));
    if (dataJson) {
      for (var i=0; i<dataJson.length; i++) {
        var candidate = new RTCIceCandidate(dataJson[i]);

        console.log("Adding ICE candidate :" + JSON.stringify(candidate) );
        this.pc.addIceCandidate(candidate).then( () =>      { console.log ("addIceCandidate OK"); }
          , (error) => { console.log ("addIceCandidate error:" + JSON.stringify(error)); } );
      }
      this.pc.addIceCandidate();
    }
  }


  /*
  * AJAX callback for Error
  */
  WebRtcStreamer.prototype.onError = function(status) {
    console.log("onError:" + status);
  }

  return WebRtcStreamer;
  })();

  if (typeof window !== 'undefined' && typeof window.document !== 'undefined') {
    window.WebRtcStreamer = WebRtcStreamer;
  }
  if (typeof module !== 'undefined' && typeof module.exports !== 'undefined') {
    module.exports = WebRtcStreamer;
  }
